I want to create a function or script, i.e CAT, which can accept
either a file name or HERE Document, as `cat' or most unix command
does.

How should I implement this function? I guess it may be related to I/O
redirection.

panruochen@gmail.com wrote:
> I want to create a function or script, i.e CAT, which can accept
> either a file name or HERE Document, as `cat' or most unix command
> does.

It is unclear what you want.


func()
{
while read -r x
do echo "'$x'"
done
}

func <<- EOT
Some text
in a here document.
EOT

func < textfile


>
> How should I implement this function? I guess it may be related to I/O
> redirection.

What shall the function do?

Janis

On 2008-03-24, panruochen@gmail.com <panruochen@gmail.com> wrote:
>
>
> I want to create a function or script, i.e CAT, which can accept
> either a file name or HERE Document, as `cat' or most unix command
> does.
>
> How should I implement this function? I guess it may be related to I/O
> redirection.

Test whether there are any arguments [ $# -ne 0 ], or any non-option
arguments if your script takes options. If a filename is given, you can
redirect input to that file, and perhaps set a variable with the filename.

On 3ÔÂ24ÈÕ, ÉÏÎç9ʱ14·Ö, Janis Papanagnou <Janis_Papanag...@hotmail.com>
wrote:
> panruoc...@gmail.com wrote:
> > I want to create a function or script, i.e CAT, which can accept
> > either a file name or HERE Document, as `cat' or most unix command
> > does.
>
> It is unclear what you want.
>
> func()
> {
> while read -r x
> do echo "'$x'"
> done
>
> }
>
> func <<- EOT
> Some text
> in a here document.
> EOT
>
> func < textfile
>
>
>
> > How should I implement this function? I guess it may be related to I/O
> > redirection.
>
> What shall the function do?
>
> Janis

I want my function, i.e CAT, act as `cat' can handle either
cat 1.txt
or
cat <<EOF
The red quick fox jumps over a lazy brown goat.
EOF

On 3ÔÂ24ÈÕ, ÉÏÎç9ʱ22·Ö, Bill Marcum <marcumb...@bellsouth.net> wrote:
> On 2008-03-24, panruoc...@gmail.com <panruoc...@gmail.com> wrote:
>
>
>
> > I want to create a function or script, i.e CAT, which can accept
> > either a file name or HERE Document, as `cat' or most unix command
> > does.
>
> > How should I implement this function? I guess it may be related to I/O
> > redirection.
>
> Test whether there are any arguments [ $# -ne 0 ], or any non-option
> arguments if your script takes options. If a filename is given, you can
> redirect input to that file, and perhaps set a variable with the filename.

what is passed to CAT if
CAT <<EOF
The red quick fox jumps over a lazy brown goat.
EOF
is excuted?

On 2008-03-24, PRC <panruochen@gmail.com> wrote:
>
>
> On 3??24??, ????9??22??, Bill Marcum <marcumb...@bellsouth.net> wrote:
>> On 2008-03-24, panruoc...@gmail.com <panruoc...@gmail.com> wrote:
>>
>>
>>
>> > I want to create a function or script, i.e CAT, which can accept
>> > either a file name or HERE Document, as `cat' or most unix command
>> > does.
>>
>> > How should I implement this function? I guess it may be related to I/O
>> > redirection.
>>
>> Test whether there are any arguments [ $# -ne 0 ], or any non-option
>> arguments if your script takes options. If a filename is given, you can
>> redirect input to that file, and perhaps set a variable with the filename.
>
> what is passed to CAT if
> CAT <<EOF
> The red quick fox jumps over a lazy brown goat.
> EOF
> is excuted?

If you write a function you can see for yourself:
CAT () {
echo "Number of arguments: $#"
echo -n "Standard input: "; cat -
}

In article
<440773ca-ae43-4c10-ae93-0e1d26f3e507@s19g2000prg.googlegroups.com>,
PRC <panruochen@gmail.com> wrote:

> On 3ÔÂ24ÈÕ, ÉÏÎç9ʱ22·Ö, Bill Marcum <marcumb...@bellsouth.net> wrote:
> > On 2008-03-24, panruoc...@gmail.com <panruoc...@gmail.com> wrote:
> >
> >
> >
> > > I want to create a function or script, i.e CAT, which can accept
> > > either a file name or HERE Document, as `cat' or most unix command
> > > does.
> >
> > > How should I implement this function? I guess it may be related to I/O
> > > redirection.
> >
> > Test whether there are any arguments [ $# -ne 0 ], or any non-option
> > arguments if your script takes options. If a filename is given, you can
> > redirect input to that file, and perhaps set a variable with the filename.
>
> what is passed to CAT if
> CAT <<EOF
> The red quick fox jumps over a lazy brown goat.
> EOF
> is excuted?

No arguments are passed. The here-document becomes the standard input
for the program. Most Unix file-processing utilities will read from
stdin if they don't get any filename arguments.

If your OS supports /dev/stdin, you can use this to simplify your script:

if [ $# -eq 0 ]
then set /dev/stdin
fi

Then the rest of your script can simply iterate over the filename
arguments.

--
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE don't copy me on replies, I'll read them in the group ***